1. Field of the Invention
The present invention relates to an air conditioning apparatus with an air cleaning function, and an electric dust collector for use in the air conditioning apparatus.
2. Description of the Related Art
To enhance the function of an air conditioning apparatus, the recent technology in this field presents a proposal in which an electric dust collector is incorporated into the room unit of the air conditioning apparatus. As well known, the electric dust collector is constructed such that a high voltage is applied to between a discharge electrode and a dust collector electrode, and the discharge electrode ionizes dust particles contained in air around the electrode, and the ionized dust particles are electrostatically attracted to the dust collector electrode. When the electric dust collector thus constructed is incorporated into the room unit of the air conditioning apparatus, the air conditioning apparatus has an air cleaning function in addition to its air conditioning function.
In the air conditioning apparatus, the electric dust collector is usually located between the front grille and the heat exchanger located on the rear side of the front grille. In other words, it is located on the front side of the heat exchanger. To increase the dust collecting efficiency of the air conditioning apparatus in which the electric dust collector is located in front of the heat exchanger, a conventional technique collects dust particles while flowing air upward in zig-zag fashion in front of the heat exchanger (Japanese Patent Unexamined Publication No. Sho. 64-28427).
On the other hand, for the cleaning of the dust collector electrode, which frequently gives rise to trouble in the electric dust collector, unique techniques have been proposed. For example, an electric dust collector of a maintenance-free type has been developed in which a heater is attached to the dust collector electrode, and dust particulate matter sticking to the electrode is burnt by the heater.
By the way, a basic structure of the electric dust collector includes the combination of a linear discharge electrode and a plate-like dust collector electrode. The structure of the conventional air conditioning apparatus in which the electric dust collector is mounted in front of the heat exchanger is disadvantageous in that the electrodes of the dust collector, particularly the plate-like dust collector electrode, hinders the attraction of air to the heat exchanger, to thereby degrade the air conditioning function, or the function inherent in the air conditioning apparatus.
That is, in this type of the air conditioning apparatus, the plate-like dust collector electrode is usually disposed above the linear discharge electrode, and along the surface of the heat exchanger. There are at least two reasons why the plate-like dust collector electrode is disposed along the surface of the heat exchanger. The first reason is to avoid an increase of the depth of the air conditioning apparatus. The second reason is to avoid such a situation that when the air conditioning apparatus carries out an air cleaning operation by weak ion stream during the rest of its air conditioning operation, the plate-like dust collector electrode hinders a smooth flow of the weak ion stream. However, the structure in which the plate-like dust collector electrode is disposed along the surface of the heat exchanger, hinders the air attraction to the heat exchanger, to thereby degrade the air conditioning function of the air conditioning apparatus.
The degradation of the air conditioning function becomes marked in the electric dust collector of the maintenance-free type in which the heater is attached to the dust collector electrode. That is, it is a common practice that the heater is used in combination with a heat shield plate or the like, in the electric dust collector of the maintenance-free type. This heater structure additionally increases an air flow resistance that is caused by the electric dust collector, and hence further impedes the attraction of air to the heat exchanger. It is for this reason that the degradation of the air conditioning function is marked in this type of the electric dust collector.
This degradation problem, which arises from the increase of the air flow resistance will be present highly probably, also in the air conditioning apparatus of the type which collects dust particles while flowing air upward in zig-zag fashion in front of the heat exchanger (Japanese Patent Unexamined Publication No. Sho. 64-28427).
Further, a periodical cleaning is required for the conventional electric dust collector to ensure its dust collecting capability. The user may clean the electric dust collector in a manner that he opens the front panel of the air conditioning apparatus and makes access to the dust collector. This cleaning style needs troublesome work.
Furthermore, another problem which will arise in designing this type of the air conditioning apparatus is how to efficiently move the dust particles contained in air flowing through the air passage toward the dust collector electrode by the utilization of electrostatic force. The ionized dust particles, which fail to stick to the dust collector electrode, will stick to an air outlet of the casing and its near portion. The dust particulate matter sticks to the flap, for example, and the flap will appear markedly dirty. Dust lumps sticking to the inside of the casing is stripped therefrom by a blow by the fan, and discharged outside through the air outlet, and floats in the room.